Defining Predation (+,-)
- An organism (predator) that consumes all or part of another organism (prey)
- benefits its own fitness
- reduces the growth, fecundity and survival of the prey population
1. True predators:
2. Grazers:
3. Parasites:

Parasitoid Bodysnatchers: complicating predator definitions…



Predator behavior is super diverse
- Behaviors to capture prey differ vastly
- consumption rate:
- consumption rate impacts populations
- True predators and grazers are mostly foragers
- searching (active foraging)
- sit and wait (passive foraging)
- Prey behavior (evasiveness) impacts consumption rate
- Parasites rely on direct transmission
- contact is density dependent

Optimal Foraging Theory
- Obtaining food provides energy
- Searching for and capturing food uses energy
- Foraging is a banking problem: Return on Investment
- To maximize fitness a forager must balance these


Optimal foraging should be related to density
- Can predators be choosy?
- Prey densities impact handling/search times
- # of foragers relates to prey density
- competition for available prey
- group foraging? (Hintz & Lonzarich 2018)
- Predators should choose to forage in a patch with the highest quality

Optimal foraging in African predators: Energy use
- Calorie use by big predators
- Cheetahs = 9,000 Kj
- Wild dogs = 15,000 Kj
- Lions = ?
- Humans = 9000 Kj
- Foraging Strategies
- Laziness
- Thievery
- Group hunting
- Seasonal prey choice

Optimal foraging in African predators: Prey choice

Consumption is an agent of natural selection: Defense

Defenses can be ‘constitutive’ of ‘induced’

Predators also adapt to prey (Cattau et al. 2017)

Predation can promote biodiversity
- If they consume the strongest competitor then the community may become more ‘even’
- Relieves competitive pressure on other species enabling coexistence
- Predation structures communities

Predator vs Prey populations (Basics)

Prey populations are always lower in the presence of predators

Impacts of predation on populations is complex…
- Behavior/adaptations of predators and prey
- Assumption of a 1 vs 1 relationship
- Life histories via reproductive traits
- Start Simple: Lynx vs Rabbit

Lotka Voltera: Modelling predator-prey dynamics
- These predator-prey patterns are described in the Lotka-Voltera 2 species model
- 2 basic components:
- P = # of predators
- N = # of prey
- Start with a lot of rabbits, who does well?
- Populations of lynx will ….
- Why does time matter at this step?
- Populations of prey will….
- Food for predators will….
- Over time predator populations will ….

Lotka-Voltera predicts coupled population cycles

Lotka Voltera equations
- With no predators,
prey populations (N) increase exponentially
- dN/dt = rN
- r = growth rate
- Predators remove prey at some rate
- dN/dt = rN - aPN
- a = attacking efficiency
-
Prey stable when dN/dt = 0
- In the absence of food,
predator populations (P) will decline
- dP/dt = -qP
- q = mortality rate
- Mortality buffered by births (faPN)
- dP/dt = faPN -qP
- food gain (aPN)
- efficiency of food to offspring (f)
-
Predator stable when dP/dt = 0